I want planet nine to be a primordial black hole so we can send a few probes out to orbit it and then chuck stuff into it to learn about quantum gravity.
Worse, since it's far away it doesn't come back to make a bigger problem for you later.
From the reference frame of the object, it falls in real time. From the reference frame of us, all time would pass before it falls in.
In other words, I don't think it would be possible to get any meaningful data from a probe within the next trillion years or so?